No oven but need pumpkin pie. Is it even possible?

I think I found a good one: http://www.kitchendaily.com/recipe/frozen-pumpkin-mousse-pie-152161. Just skip the oven step.

A prebaked crust (preferably a crumb crust, pumpkin mousse as filling -- smooth, chill, serve with whipped cream.

If it's pumpkin pie you must have (not mousse, or any of the other good suggestions from other posters) - I suggest going to a good bakery and pick one up. It will be better than pie you could hack without an oven!

Suggestion #1: Go to the bakery. Buy a pie.

But if that's not possible or / and you like a challenge like me, you can still bake a pie without an oven as long as you have a few basic kitchen implements. You'll need a pie plate of course (or a suitable substitution) and a large stock pot or similar vessel, the larger the better.

Line your baking dish with pastry dough. Crumple some aluminum foil into balls a couple of inches in diameter. Place the foil balls on the bottom of the pot so as to elevate the pie dish and keep it off the bottom while it bakes. There are other things you could use for the purpose such as cans with the tops and bottoms cut out of them, bent wire coat hangers -- anything to promote easy air flow under the pie.

Put the pot on the stove, hang a thermometer probe inside if you've got one, cover and crank up the heat. You'll have to keep a close eye on things and be your own thermostat, regulating the burner as necessary to maintain temperature. Prepare your filling and repeat.

Thought you might enjoy this pumpkin mousse instead:
http://www.nytimes.com/2012/11/19/health/to-end-the-feast-something-sweet-but-light-recipes-for-health.html?ref=health&_r=0

As mentioned, you can do a graham cracker crust and use either a pumpkin/cheesecake or pumpkin pudding mixture as the filling.
A pumpkin trifle might be another option, though you'd probably have to opt for pumpkin bread or some other type of cake from your bakery or market.
Alternatively, you can make a pumpkin ice cream, served with roasted pumpkin or pumpkin seeds, granola, or any other topping you like.

You could also try a pumpkin mousse:
http://www.food52.com/recipes/7559_ricotta_and_pumpkin_mousse_parfaits
http://www.food52.com/recipes/7723_pumpkin_mousse

A typical pumpkin pie is an egg custard, so you need to bake & set the eggs in some way - for food safety and texture reasons.

If you have a stovetop, you could possibly make a pumpkin cheesecake or pie filling-esque custard in a slow hot water bath (bain marie). Put the filling in a springform pan, lined tightly with cling film and then 2 layers of aluminum foil, or in individual ramekins and place in a pan with 4" sides. Fill the pan with hot, recently boiled water about 1/2 way up the sides of the dish(es) and cover the pan with foil. Keep on low heat and make sure the water continues to simmer while the custard bakes.

This won't work for a dessert with a traditional flaky pie crust, but you could maybe use a shards of pre-baked pie crust/puff pastry as a garnish or do a graham cracker crust base.

Do you mean can you "bake" one on the stovetop instead? Probably not, since you won't be able to get an even, constant heat. What you can do is something like a set custard pie that doesn't need to be baked; buy a pre-made pie crust, and cook the filling, pour it into the crust and chill before serving. I haven't tried this one myself but I found it on allrecipes.com: http://allrecipes.com/Recipe/no-bake-pumpkin-pie-i/detail.aspx